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Fat demythologized?

Gabriel BorrudFebruary 11, 2015

A new study could break apart long-standing guidelines on what constitutes a healthy diet. For decades, people have been told how much fat they should eat. DW has the skinny.

https://p.dw.com/p/1EZDa
Hamburger (dpa)
Image: picture-alliance/dpa

Since 1977 in the United States and 1983 in Britain, consensus regarding the dangers of eating too much fat has been a guiding principle for how people there fill their nutritional pyramids.

What is the basis for that consensus? Not science, says a Ph.D. candidate at the University of the West of Scotland (UWS), who has just been published in the journal "Open Heart," alleging that the initial claims were not supported by - and even contradicted - trial evidence.

Zoe Harcombe, who worked with colleagues at UWS and James DiNicolantonio of Saint Luke's Mid America Heart Institute in Kansas, write that the evidence available at the time "did not support the introduction of dietary fat recommendations in order to reduce [coronary heart disease] risk or related mortality."

Harcombe calls it "incomprehensible" that nutritional guidelines were given to millions of people based on "contrary results."

The study, published Monday, is a meta-analysis of six nutritional trials conducted before 1983, comprising 2467 men who took part in dietary interventions spanning an average of five years.

Five of the six groups neglected the dietary guidelines (treatment groups) with regard to total fat intake and saturated fat intake, the researchers write, but there were no visible differences with regard to cholesterol levels or mortality rates.

"There was no difference in deaths from all causes between the treatment and comparison groups, with 370 deaths in both. And there was no significant difference in deaths from coronary heart disease, with 207 in the treatment groups and 216 in the comparison groups," the researchers say.

PUBLIC DOMAIN
At least 55 percent starch, at most 30 percent fat - the USDA food pyramid as taught to kids from 1st grade onImage: ORF

Focus on fat?

In 1977, a bipartisan US Senate committee that had heard extensive testimony from physicians and nutritional specialists came up with the "Dietary Goals for the United States," a recommendation that would single-handedly influence nutritional policy for decades in the United States and by extension Britain, which adopted the guidelines six years later.

The report, which recommends increasing carbohydrate intake to 55-60 percent of daily calories, warned that "there is a great deal of evidence and it continues to accumulate, which strongly implicates and, in some instances, proves that the major causes of death and disability in the United States are related to the diet we eat." The three main nutritional elements that lead to coronary heart disease, the report concluded, were meat, fat and, in particular, saturated fat.

Despite the Senate report and the public consensus that followed, the American Heart Association (AHA) has since throttled back its warnings against fat consumption.

Though the AHA does officially still recommend that total fat should not exceed 30 percent of daily calorie intake, its latest scientific statement places more of an emphasis on saturated fats with regard to the risk of coronary disease and "sudden cardiac death."

In its concluding "major guidelines" for ensuring overall coronary health and maintaining healthy weight, the scientific statement doesn't mention total fat intake at all.

"Match intake of energy (calories) to overall energy needs; limit consumption of foods with a high caloric density and/or low nutritional quality, including those with a high content of sugars. Limit the intake of foods with a high content of saturated fatty acids and cholesterol. Substitute grains and unsaturated fatty acids from vegetables, fish, legumes, and nuts."

Not so fast…

The publication of Harcombe's study met with immediate criticism from a leading British nutritional expert, who urges "extreme caution" when it comes to concluding that the health warnings were "wrong."

Christine Williams, professor of human nutrition at Reading University, said in a statement to the Reuters news agency that "the claim that guidelines on dietary fat introduced in the 1970s and 80s were not based on good scientific evidence is misguided and potentially dangerous."

Heart
Fats are thought to have particularly adverse effects on the human heartImage: Fotolia

The study, though, was published along with an editorial by Rahul Bahl, of the Royal Berkshire NHS Foundation Trust, who himself expressed the need for caution when making such potentially far-reaching claims.

Saying that the study rightly pointed out the "very limited" extent to which dietary guidelines are based on strong evidence, Bahl still insisted: "This doesn't mean that the risk factor identified is not a true risk factor."